1. Field of the Invention
The invention relates to an apparatus, system, and method for punching holes in the walls of elongate hollow bodies. In particular, the invention relates to an apparatus, system, and method for die punching holes in the walls of elongate hollow bodies by use of an expandable die which is insertable into the elongate hollow body and positionable anywhere along the length of the elongate hollow body.
2. Description of the Prior Art
There has long existed a need to be able to economically and reliably die punch holes at desired locations along the length of elongate hollow bodies. For example, in the architectural glass industry, elongate hollow bodies in the form of aluminum mullions up to thirty feet in length are used for supporting panels of architectural glass. Cross-members and associated hardware are attached to the mullions by way of fasteners such as screws and bolts. The holes in the mullions for receiving the fasteners must be precisely located and reliably sized to provide for the fit and structural integrity necessary for the assembled architectural structure. Moreover, the mullion surface is often exposed to view making its surface finish an aesthetically important feature.
Two methods have been commonly employed for making the holes in such mullions. One way is to make the holes by use of a rotary tool such as drilling or routering. Rotary tool hole-making can be done in a shop, but is time consuming and produces shavings which present cleanup problems. Rotary tool hole-making can also be done in the field, but the hole location is not as precise and the sizing as reliable as they are for shop-made holes. Furthermore, the surface of the mullion may become scratched or dented during such hole-making processes. Moreover, even when done in a shop, rotary tool hole-making is a relatively slow and expensive process and the hole shape is limited to being generally round.
The other commonly used way of making holes in a mullion is to use die punching in conjunction with an open body such as an open-side extrusion. This method requires that the mullion consists of two or more longitudinal pieces that may be joined together during service, but which during hole punching are separate and apart so that each piece has at least one open side. The open side permits the piece to be fit over a conventional punch die anvil. This method allows reliably sized holes of a desired shape to be die punched at precise locations along the length of the mullion. However, this method is not suitable for use with a single-piece elongate hollow body and the use of a multi-piece assembly is more expensive than the use of a single-piece extrusion.
There are other methods which have also been employed in the past for punching holes into elongate hollow bodies, but each of these has its own drawbacks. For example, Duce, U.S. Pat. No. 4,744,276, issued May 17, 1988, describes a method and an apparatus which use an exterior punch in combination with a die contained in a solid mandrel. This solid mandrel is inserted into the interior of a square tube with very little clearance. This method has the disadvantage that the mandrel must be sized to have a cross-section which approximates the interior cross-sectional dimensions of the elongate hollow body closely enough to avoid any collapse or deformation of the hollow body during the pressing operation. Thus, a separate mandrel is needed for each hollow body interior cross-section. Another disadvantage is that size variances and straightness irregularities in the interior of the elongate hollow body may make it difficult or impossible to employ this method. Woodward, U.S. Pat. No. 3,209,575, issued Oct. 5, 1965, also teaches the use of a solid mandrel, and, thus, is similarly disadvantaged.
Coulon et al., U.S. Pat. No. 3,698,274, issued Oct. 17, 1972, uses an exterior punch in combination with a die contained within a longitudinally split mandrel. The ends of the split-mandrel which are remote from the die are fixedly anchored. A wedge is forced between the two mandrel halves at their ends which are proximate to the die so as to make them engage the top and bottom interior surfaces of the tubular body that is to be punched. Although this method allows the same split-mandrel to be used for a range of tube diameters, it suffers from the obvious disadvantage of requiring the use of large amounts of material to make the mandrel and difficulties in supporting the mandrel for long elongate hollow bodies. Furthermore, this method is somewhat sensitive to the straightness of the interior of the hollow body.
Aizaki et al., U.S. Pat. No. 5,140,881, issued Aug. 25, 1992, describes an apparatus which uses an interior punch in combination with an exterior die to punch a hole in the sidewall of a cylinder from the inside out. The punch mechanism is contained within a sleeve tube that fits inside the cylinder that is to be punched. The punch mechanism consists of a radially-situated, floating punch, a bar-like cam supporting the floating punch, and a cylindrical member slidably inserted into the sleeve tube. The cylindrical member is attached to the bar-like cam at one end and at the other to a device which can axially reciprocate the cylindrical-member within the sleeve tube so as to cause the bar-like cam to force the floating punch radially outward through the cylinder wall and into the exterior die and then radially inward withdrawing the floating punch from the cylinder wall. Although this apparatus could conceivably be adapted to shapes other than cylinders, it has the disadvantage that the sleeve must be sized to closely approximate the interior size of the hollow body to be punched. Thus, uniformities in interior straightness and size of the hollow body are important constraints on the operation of this method. This method also has the disadvantage that, for long elongate hollow bodies, the punch mechanism is cumbersome and relatively expensive.
The present invention comprises a novel apparatus, system, and method for satisfying the need for economically and reliably punching holes along the length of elongate hollow bodies of any shape and length while overcoming the disadvantages inherent in the prior art devices described above.
The apparatus of the present invention comprises an expandable die that is insertable into the elongate hollow body. In operation, the expandable die cooperates with the punch or punches of an external conventional punch press. The expandable die is connected to the free end of a longitudinal member. The longitudinal member is hereinafter referred to as the positioning bar because it is used to longitudinally position the expandable die in relation to the punch or punches of the punch press. The distal end of the positioning bar is fixed in relation to the punch press. Preferably, the positioning bar is attached to a conventional support table and the attachment is made in a manner that allows for adjusting and then locking the longitudinal position of the expandable die with respect to the punch or punches of the punch press.
The expandable die is inserted into the elongate hollow body by sliding the hollow body through the gap between the expandable die and the punches of the punch press to the location where a hole or set of holes is to be punched. The expandable die has a die member which has one or more die cavities for receiving the punch or punches of the punch press. The cross-sectional shapes and sizes of the die cavities and the punches are made to produce the desired shape and size of hole or holes that are to be punched. Such cross-sectional shapes may be circular or non-circular so that a circular or a non-circular hole is punched, respectively. The expandable die also has a base member. The die and base members are designed so as to cooperate in supporting the elongate hollow body during the punching operation in a manner which prevents the elongate hollow body from becoming dented or otherwise damaged. Preferably, the outside surfaces of the die and base members are shaped to fit the contour of the corresponding inside surfaces of the elongate hollow body to better enable these members to provide sufficient support during the pressing operation to prevent the elongate hollow body from being deformed.
The expandable die also comprises an expansion mechanism, for example, without limitation, an expansion engine and a retractable support mechanism, for moving either or both of the die and base members outwardly to supportingly engage the adjacent inside surfaces of the hollow body during the punching operation and for moving either or both of these members inwardly after the punching operation has been completed. In the expanded position, which is also referred to herein as the activated position, the expandable die provides sufficient support to the elongate hollow body to prevent the punch or punches from denting or deforming the hollow body. In some embodiments this support is rigid and may be supplied in whole or in part by a retractable support mechanism. The expandable die also has at least one mechanism, for example, without limitation, an extendable piston, for laterally aligning the expandable die in relation to the punch or punches of the punch press. Preferably, the expandable die also comprises a receptacle for receiving the punch offal.
The system comprises an expandable single- or multiple-cavity die in combination with a conventional punch press having single or multiple punches. The system may also comprise a conventional static or roller table for supporting, backing or positioning the elongate hollow body.
When a support table is employed as part of a system according to the present invention, it is preferred that the support table include a guide for laterally positioning the elongate hollow body with respect to the punch or punches of the conventional punch press. The system may also include a mechanism for longitudinally moving the elongate hollow body after punching to the location where the next hole or set of holes is to be punched.
The method includes the steps of: (1) longitudinally aligning an expandable die with respect to at least one punch of a punch press, the expandable die having a die member and a base member and at least one die cavity in the die member for receiving the punch or punches of the punch press; (2) inserting the expandable die into an elongate hollow body; (3) activating the expandable die so that the die cavity or cavities become laterally aligned with the punch or punches and so that the die and base members of the expandable die come into supporting contact with the inside surfaces of the elongate hollow body; and (4) operating the punch press so that one or more holes are punched through the wall of the elongate hollow body. As used herein, the term supporting contact is used to mean that the die and base outer surfaces of the expandable die contact adjacent inside surfaces of the elongate hollow body in such a manner that the expandable die prevents the elongate hollow body from becoming dented or deformed during the pressing operation. After a hole or set of holes has been punched, the elongate hollow body can then be moved to the next position where a hole or set of holes are to be punched. Preferably, the expandable die is retracted after step (4) so as to make it easier to move the elongate hollow body in relation to the expandable die. As used herein, the term retract means to operate the expandable die in a manner which withdraws the lateral positioning mechanism and/or the die and/or base members of the expandable die from contact with the interior surfaces of the elongate hollow body sufficiently to allow the elongate hollow body to be moved with respect to the expandable die without causing damage to either the expandable die or the elongate hollow body.
Other features and advantages inherent in the subject matter claimed and disclosed will become apparent to those skilled in the art from the following detailed description of presently preferred embodiments thereof and to the appended drawings.